public class Test3 {
    public static void main(String[] args) {
        System.out.println(count());
    }

    public static double count(){
        double sum = 0;
        for (int i = 1; i <= 100; i++) {
            if(i % 2 == 0){
                sum = sum - 1.0 / i;
            }else{
                sum = sum + 1.0 / i;
            }
        }
        return sum;
    }
}


